Gene Regulation and Systems Biology

Makoto Umemori¹, Okiko Habara², Tatsunori Iwata³, Kousuke Maeda¹, Kana Nishinoue⁴, Atsushi Okabe³, Masahiko Takemura¹, Kuniaki Takahashi⁵, Kaoru Saigo⁶, Ryu Ueda⁵ and Takashi Adachi-Yamada^1,2,3,4

¹Department of Biology, Graduate School of Science, Kobe University, Kobe, Japan. ²Japan Science and Technology Agency, Japan. ³Department of Sciences for Natural Environment, Graduate School of Cultural Studies and Human Science, Kobe University, Kobe, Japan. ⁴Department of Sciences for Natural Environment, Faculty of Human Development, Kobe University, Kobe, Japan. ⁵Genetic Strains Research Center, National Institute of Genetics, Mishima, Japan. ⁶Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Tokyo, Japan.

Abstract

The genetically amenable organism Drosophila melanogaster has been estimated to have 14,076 protein coding genes in the genome, according to the flybase release note R5.13 (http://fl ybase.bio.indiana.edu/static_pages/docs/ release_notes.html). Recent application of RNA interference (RNAi) to the study of developmental biology in Drosophila has enabled us to carry out a systematic investigation of genes affecting various specific phenotypes. In order to search for genes supporting cell survival, we conducted an immunohistochemical examination in which the RNAi of 2,497 genes was independently induced within the dorsal compartment of the wing imaginal disc. Under these conditions, the activities of a stress-activated protein kinase JNK (c-Jun N-terminal kinase) and apoptosis-executing factor Caspase-3 were monitored. Approximately half of the genes displayed a strong JNK or Caspase-3 activation when their RNAi was induced. Most of the JNK activation accompanied Caspase-3 activation, while the opposite did not hold true. Interestingly, the area activating Caspase-3 was more broadly seen than that activating JNK, suggesting that JNK is crucial for induction of non-autonomous apoptosis in many cases. Furthermore, the RNAi of essential factors commonly regulating transcription and translation showed a severe and cell-autonomous apoptosis but also elicited another apoptosis at an adjacent area in a non-autonomous way. We also found that the frequency of apoptosis varies depending on the tissues.